JPH0237131A - Fuel supply control device of engine - Google Patents

Abstract

PURPOSE:To lower the temperature of exhaust gas without deterioration of fuel cost by decreasing the gasoline supply amount when the temperature of exhaust gas is above a designated temperature to increase the gas fuel supply amount. CONSTITUTION:In an ECU 40, it is judged from a value of an intake air negative pressure sensor 11 whether the operation range is in a high load range or in a low load range. Secondly, it is judged from a signal of an igniter 13 whether it is in high rotation or low rotation range. Further, it is judged by an exhaust gas temperature sensor 12 whether the exhaust gas temperature exceeds a designated valve or not. According to the judgement, when the exhaust gas temperature exceeds a designated value in the low load range or in the high load-high rotation range, a solenoid 32 is opened and a solenoid 23 is closed to select LPG as fuel. Accordingly, it is not necessary to control the supply on rich side uniformly in high load range for holding down the exhaust gas temperature, and the exhaust gas temperature is made lower than the exhaust gas temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel supply control device for an engine, particularly to a fuel supply control device for an engine that uses both gas fuel and gasoline.

[Prior Art] Conventionally, there are engines that switch between gas fuel (for example, LPG) and gasoline. Although LPG is cheap, it is supplied to the engine in a gaseous state, which reduces the amount of fresh air and makes it impossible to obtain high output.However, due to its high octane rating, knocking is less likely to occur even at high compression ratios.
By increasing the compression ratio, fuel efficiency (economic efficiency) can be further improved. On the other hand, since gasoline is supplied in liquid form, it has a large amount of fresh air and high filling efficiency, making it possible to obtain high output, but on the other hand, it has a lower beoctane number compared to LPG and is more likely to cause knocking if the compression ratio is increased. It's expensive. Generally, gasoline is used for high loads and LPG for low loads.
supply.

In JP-A No. 59-101560, in order to solve the problem that the optimum compression ratios are different for LPG and gasoline, and the advantages of both cannot be fully utilized by switching at a constant compression ratio,
Depending on the switching use between LPG and gasoline, the compression ratio of the engine is adjusted to the compression ratio suitable for each state, and the LPG
This improves fuel efficiency by increasing the combustion efficiency of the engine, and prevents knocking when using gasoline, ensuring good drivability.

[Problem to be solved by the invention] However, considering the temperature of the exhaust gas, the gas fuel is supplied in a gaseous state, so the engine can be operated at a relatively low temperature, and the amount of intake air can be suppressed, so it is difficult to achieve high output. First, the temperature of the exhaust gas does not rise.

On the other hand, since gasoline is supplied in a liquid state, the amount of intake air increases, resulting in high output and extremely high exhaust gas temperature.

Therefore, in high-load and high-speed ranges, the air-heat ratio is uniformly controlled to the rich side in order to suppress the temperature of exhaust gas, which is also disadvantageous in terms of fuel efficiency.

The present invention provides an engine fuel supply control device that eliminates the above-mentioned conventional drawbacks and lowers the temperature of exhaust gas in an engine that uses both gas fuel and gasoline without causing deterioration of fuel efficiency.

[Means for Solving the Problem] As a means for solving the problem, the fuel supply control device of the present invention, as shown in FIG. and a fuel supply control means 3 that reduces the gasoline supply amount and increases the gas fuel supply amount when the temperature of the exhaust gas detected by the temperature detection means 5 is higher than a predetermined temperature. .

[Function] In this configuration, the temperature detection means 5 detects the exhaust gas temperature from the engine body 1, and when the exhaust gas temperature is higher than a predetermined temperature, the fuel supply control means 3 reduces the amount of gasoline supplied from the gasoline supply section 1. Then, the amount of gas supplied from the gas fuel supply unit 2 is increased.

[Example] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a diagram showing the configuration of the engine of this embodiment. In the figure, 10 is an engine body, and an intake negative pressure sensor 11 is installed on the intake side, and an exhaust temperature sensor 12'' is installed on the exhaust side. Also, the engine rotation speed is known from the igniter 13. Reference numeral 20 denotes a gasoline supply mechanism, which includes a gasoline tank 21, a gasoline pump 22 for supply, and a solenoid 23 for adjusting the supply amount. On the other hand, 30 is an LPG supply mechanism, which includes an LPG cylinder 31, a solenoid 32 for adjusting the supply amount, a pre-heater 33 for heating, and a vaporizer 34 for regulating vaporization pressure.

4o is the engine control unit that controls the engine.
The control unit (ECU) consists of a microprocessor that operates according to a predetermined control program including the flowchart shown in FIG.

The ECU 40 generally detects the engine load based on the negative pressure from the intake negative pressure sensor 11, selects gasoline in a high load range, selects LPG in a low load range, and selects each solenoid 23.
．． Controls the opening and closing of 32. In this example, a case of switching will be described, but control may also be performed by changing the mixing ratio by using a combination of the two.

In this embodiment, even in the high load range, if the exhaust temperature from the exhaust temperature sensor 12 exceeds a predetermined value, the solenoid 23 is closed, the solenoid 32 is opened, and the
Use PG. Note that the exhaust gas temperature may be measured without using the sensor 13 as in this embodiment, and it may be determined that the exhaust gas temperature reaches a high temperature when a predetermined time has elapsed after entering a high load. LP
By using G, the exhaust temperature decreases, and there is no need to control the temperature decrease due to the conventional shift to the rich side, and wasteful use of fuel can be eliminated.

FIG. 3 is a flowchart of a control program related to the present invention in this embodiment.

First, in step SIO, it is determined whether the operating range is a high load range or a low load range based on the value from the intake negative pressure sensor 11. Next, in step S12, it is determined whether the engine is in a high rotation range or a low rotation range based on a signal from the igniter 13. Furthermore, in step S14, the exhaust gas temperature sensor 12 determines whether the exhaust gas temperature exceeds a predetermined value T0.

Above steps SIO, S12. If the exhaust gas temperature exceeds the predetermined value in the low load range or high load/high rotation range as determined in S14, the process proceeds to step S18, where the solenoid 32 is opened and the solenoid 23 is closed to use LPG as fuel. If the exhaust gas temperature does not exceed the predetermined value in the high load/low rotation range or the high load/high rotation range, the solenoid 32 is closed and the solenoid 23 is opened in step S16 to select gasoline as the fuel. do.

With the above control, there is no need to uniformly control the exhaust gas temperature to the rich side in the high load range in order to suppress the exhaust gas temperature, and the exhaust gas temperature can be lowered below the predetermined temperature. Note that the flowchart in FIG. 3 is a simplified example, and the switching control between gasoline and LPG is not limited to this.

[Effects of the Invention] According to the present invention, it is possible to provide a fuel supply control device for an engine that lowers the temperature of exhaust gas without deteriorating fuel efficiency in an engine that uses both gas fuel and gasoline.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the fuel supply control device of the present invention, FIG. 2 is a diagram showing the configuration of the engine of the present embodiment, and FIG. 3 is a flowchart of the control program of the ECU of the present embodiment. In the figure, 1... Gasoline supply section, 2... Gas fuel supply section, 3... Fuel supply control means, 4... Engine body, 5... Temperature detection means, 10... Engine body ,1
1... Intake negative pressure sensor, 12... Exhaust temperature sensor,
13...Igniter, 20...Gasoline supply mechanism,
21...Gasoline tank, 22...Gasoline pump, 23...Solenoid, 30...Gas fuel supply mechanism, 31...LPG cylinder, 32...Solenoid, 3
3... Preheater, 34... Paper riser 4
0...ECU. , 子已Vsu〉上 Yi 1; J Fig. 3

Claims (1)

[Claims] In an engine that uses both gas fuel and gasoline, there is provided a temperature detection means for detecting the temperature of exhaust gas, and when the temperature of the exhaust gas detected by the temperature detection means is higher than a predetermined temperature, the amount of gasoline supplied is reduced. 1. A fuel supply control device for an engine, comprising: fuel supply control means for decreasing the gas fuel supply amount and increasing the gas fuel supply amount.